c++ - 如何在另一个函数中使用一个函数？

Question

我有两个.cpp 文件，一个叫practice.cpp，另一个叫adder.cpp。它们都在 Source Files 文件夹中。

拳头代码如下:

// adder.cpp

#include "stdafx.h" //include library


int addition(int a, int b) //start function
{
    int r = 0; //declare variables
    r = a + b; //actual code
    return r; //output of function
}

第二个代码:

// Practice.cpp

#include "stdafx.h"
#include "adder.cpp"
#include <iostream>
using namespace std;


int main(void)
{
    int number1 = 0;
    int number2 = 0;
    int number3 = 0;

    do 
    {
        printf("\n\nInsert value for first number\n\n");
        scanf("%d",&number1);

        printf("\nthe value ");
        printf("%d ",number1);
        printf("has been stored in memory location ");
        printf("%d",&number1);

        printf("\n\nInsert value for second number\n\n");
        scanf("%d",&number2);

        printf("\nthe value ");
        printf("%d ",number2);
        printf("has been stored in memory location ");
        printf("%d",&number2);

        number3 = addition(number1,number2);

        printf("%d",number3);



    }
    while (1==1);

    return 0;
}

但是代码不会编译。我收到错误:

1>------ Build started: Project: Practice, Configuration: Debug Win32 ------
1>  Practice.cpp
1>c:\users\craig\documents\3rd year work\progamable     systems\practice\practice\practice.cpp(25): warning C4996: 'scanf': This function or     variable may be unsafe. Consider using scanf_s instead. To disable deprecation, use     _CRT_SECURE_NO_WARNINGS. See online help for details.
1>          c:\program files (x86)\microsoft visual studio 10.0\vc\include\stdio.h(304)     : see declaration of 'scanf'
1>c:\users\craig\documents\3rd year work\progamable     systems\practice\practice\practice.cpp(33): warning C4996: 'scanf': This function or     variable may be unsafe. Consider using scanf_s instead. To disable deprecation, use     _CRT_SECURE_NO_WARNINGS. See online help for details.
1>          c:\program files (x86)\microsoft visual studio 10.0\vc\include\stdio.h(304)     : see declaration of 'scanf'
1>Practice.obj : error LNK2005: "int __cdecl addition(int,int)" (?addition@@YAHHH@Z)     already defined in adder.obj
1>C:\Users\Craig\Documents\3rd year work\Progamable Systems\Practice\Debug\Practice.exe     : fatal error LNK1169: one or more multiply defined symbols found
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

我一直在网上寻找，但看起来我做得对。我该怎么做才能解决这个问题？谢谢!

Answer 1

不要包含 .cpp 文件，这就是编译器告诉您多个定义的原因。您必须创建一个 header .h 文件并将其包含在您的两个 .cpp 文件中，并放入以下内容:

// adder.h

#ifndef ADDER_H
#define ADDER_H

int addition(int, int);

#endif

预处理器语句会告诉编译器只定义一次方法addition。成功了，祝你好运:)